Protein farnesyltransferase (FTase)_like proteins containing the protein prenyltransferase (PTase) domain, beta subunit (alpha 6 - alpha 6 barrel fold). FTases are a subgroup of PTase family of lipid-modifying enzymes. PTases catalyze the carboxyl-terminal lipidation of Ras, Rab, and several other cellular signal transduction proteins, facilitating membrane associations and specific protein-protein interactions. These proteins are heterodimers of alpha and beta subunits. Both subunits are required for catalytic activity. Prenyltransferases employ a Zn2+ ion to alkylate a thiol group catalyzing the formation of thioether linkages between cysteine residues at or near the C-terminus of protein acceptors and the C1 atom of isoprenoid lipids. Ftase attaches a 15-carbon farnesyl group to the cysteine within the C-terminal CaaX motif of substrate proteins when X is Ala, Met, Ser, Cys or Gln. Protein farnesylation has been shown to play critical roles in a variety of cellular processes including Ras/mitogen activated protein kinase signaling pathways in mammals and, abscisic acid signal transduction in Arabidopsis.
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